'Super Earth': the exoplanet in the 'habitable zone' for alien life

"If extraterrestrials do exist, scientists have found a promising location for where they could be hiding," said the Daily Mail. Named HD 20794 D, the newly discovered exoplanet orbits a star similar to the Sun, and researchers believe it may be able to sustain liquid water, which is vital for life, as we know it, to exist.

"Best of all," added the Mail, it lies just 19.7 light-years away from Earth, raising the "tantalising possibility" of being able to photograph it and, of course, "any aliens lurking there".

What is an exoplanet? 

An exoplanet is a planet outside our solar system that usually orbits a star in our galaxy. More than 7,000 have been found in the Milky Way since the first confirmed discovery in the 1990s, and "billions more remain to be discovered", said Tech Explorist.

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Most of the exoplanets that have been found are within a small region of the galaxy – "'small' meaning within thousands of light-years of our solar system", said Nasa, which is as far as current telescopes are able to penetrate. One light-year is the equivalent of 5.88 trillion miles.

How was the new exoplanet found?

Methods used to find exoplanets include "watching for wobble" – that is, the changes in the light emitted by a star when it makes a tiny movement due to the gravitational tug of a passing planet.

In 2022, Dr Michael Cretignier, from the University of Oxford, spotted periodic changes in the light being emitted by the star HD 20794 D. The faintness of the signal made it difficult to confirm the presence of an exoplanet, with a chance the signal was instead the result of instrument error. The team spent the next two years analysing "highly precise measurements" from more than 20 years of data from the region to prove his theory, said the University of Oxford in a press release.

"For me, it was naturally a huge joy when we could confirm the planet’s existence," said Cretignier. "It was also a relief."

This prolonged study of the star's movement also allowed scientists to determine the planet's size as six times the mass of Earth – "the larger the wobble, the greater the mass", said Space.com.

Could life exist on HD 20794 D?

HD 20794 D is located within the so-called "Goldilocks zone", where temperatures would support the presence of liquid water, a prerequisite for life.

"Having a planet in the habitable zone is not sufficient at all to have life on it," Cretignier told the Daily Mail. "Both Mars and Venus are inside the habitable zone of the sun, but I highly don't recommend you to go there on holiday."

Unlike the circular orbit of most planets, HD 20794 D follows an elliptical orbit more elongated than any of the planets in our solar system. This means it moves from the outer edge of the habitable zone to the inner region during its 647-day journey around the star.

Winters would be "long and hard" in this "bizarre" climate, said Space.com, with any life struggling to survive on a planet that spends so much time frozen. But even if life does not exist on HD 20794 D, its strange orbit will provide an "invaluable test case" for future studies, said the University of Oxford.